Dual encoders are input apparatuses, which allow users to enter an assigned electrical signal by turning an activation element. Here, dual encoders are characterized in that they do not only include one activation element, for instance a rotary knob or a rotary disk, but two activation elements. Here, both activation elements are connected to a shaft being mounted so as to be rotatable. One rotation signal generator, which is able to directly or indirectly detect a turning of the shaft, is assigned to each shaft. In each instance, the two rotation signal generators then generate an electrical signal after having detected an adjusting movement at the shaft.
Besides, the two shafts are equipped with one locking mechanism in each instance, which mechanism is able to lock the shafts in different rotational positions. In this manner, the signals having been generated by the rotation signal generator can show a switchover between two locking positions by turning the shaft.
For instance, but by no means exclusively, known dual encoders may be used for entering two adjusting values at an appliance, for instance the X value and the Y value in a Cartesian coordinate system, with discrete rates in each instance, with only minor adjusting movements of the hand. From document DE 33 36 746 A1, a simple encoder is known, which is embodied in the manner of a rotary switch. Said encoder has a mechanical locking mechanism, which is able to fix the shaft in different locking positions. Said mechanical locking mechanism has the disadvantage that the mechanical connections of the locking mechanism are subject to relatively high wear, due to which the locking mechanism becomes sluggish or fails completely after a certain running time.